It could be a sign just of how much Ron respects Leslie that he brings them up to her. I mean, it's only happened a few times as well. There's also the time skip happening. I think it would be easy for Ben or Andy to suddenly get a bit weirded out about not knowing even if they had a couple of passing references over the years. It is weird in the context of a tv show, though. It would have been better payoff if we the viewer didn't know about them either, which is why the joke may fall a little flat for people (I had just marathoned everything before marathoning the final season so it was all fresh on my mind).

The accounting firm would have been good. I think it would have been kind of funny to have one of the triplets go to the accounting firm to get a job and have them get so excited to get Ben's kid, only to have him/her decide against it or quit. Continue the tradition! At the same time, that joke was played up a bit too much and maybe it would have been more fitting to get a Cones of Dunshire thing going with them.

Added character scenes in the Producer's Cut of the finale for anyone interested Shauna Malwae-Tweep, Bobby Newport, a bit of Councilman Jam. Also a couple of scenes are extended with one funny one and a couple of that seem to go on for a little too long. It would be worth watching if you haven't yet. It's on hulu!